• Advances in aircraft and spacecraft science
• /
• 제5권3호
• /
• pp.319-334
• /
• 2018

In this study, the failure mode and energy absorption capabilities of a composite shock absorber device, during an emergency landing are evaluated. The prototype has been installed and tested in laboratory simulating an emergency landing test condition. The crash absorber presents an innovative configuration able to reduce the loads transmitted to a helicopter fuselage during an emergency landing. It consists of a composite tailored tube installed on the landing gear strut. During an emergency landing this crash absorber system should be able to absorb energy through a pre-designed deformation. This solution, compared to an oleo-pneumatic shock absorber, avoids sealing checks, very high values of the shock absorber pressure, and results to be lighter, easy in maintenance, inspect and use. The activities reported in this paper have become an attractive research field both from the scientific viewpoint and the prospect of industrial applications, because they offer benefits in terms of energy absorbing, weight savings, increasing the safety levels, and finally reducing the costs in a global sense.

• 한국조경학회지
• /
• 제28권1호
• /
• pp.136-146
• /
• 2000

Although the urban elevated road is welcomed in modern society to deal with urban traffic problems, its negative influence on both the pedestrian environment and urban landscape has been frequently observed. Furthermore, the space under elevated structures has been ignored, being the lost space. Recently, several efforts have been devoted into bringing back the lostspace. However, any specific design guidelines shown in the street design of Japan and Singapore have not been suggested in Korea, yet. This study proposes a case of the Nengdong-Ro street design where the two-story urban elevated road is being constructed and negative effects of the elevated road are largely expected. One of the purposes of Nengdong-Ro street design proposed in this study is to relieve the negative effect os the two-story elevated road, and to provide a better pedestrian environment in Nengdong-Ro. The other purpose is to suggest general guidelines that can be applied to the similar context as Nengdong-Ro. It is considered that the space under the elevated road generally consist of three sections: 1) main section where the elevated road runs parallel with the ground, 2) landing section where elevated road goes down to the ground, and 3) facility section where facilities such as the platform and the ticketing booth are located. The design guidelines are suggested for each section, because each section has a different situation. Plans, section and elevations and the details of the street furniture are also incorporated to support the design guidelines.

• 한국운동역학회지
• /
• 제32권1호
• /
• pp.24-30
• /
• 2022

Objective: The purpose of this study was to determine the factors of successful and unsuccessful movements through the analysis of kinematics and muscle activity of the Free Aerial Cartwheel on the balance beam. Method: Subjects (Age: 22.8 ± 2.4 yrs., Height: 158.7 ± 5.0 cm, Body mass: 54.1 ± 6.4 kg, Career: 13 ± 2.4 yrs.) who were currently active as female gymnasts participated in the study. They had no history of surgical treatment within 3 months. Subject criteria included more than 10 years of professional experience in college and professional level of gymnastics and the ability to conduct the Free Aerial Cartwheel on the Balance Beam. Each subject performed 10 times of Free Aerial Cartwheel on the balance beam. One successful trial and one unsuccessful trial (failure) among 10 trials were selected for the comparison. Results: It was found that longer time required in case of unsuccessful trial when performing the Free Aerial Cartwheel on the balance beam compared with successful trial. It is expected to be the result of movement in the last landing section (i.e. phase 5). In addition, it was found that the center of gravity of the body descends at a high speed to perform the jump (i.e. phase 2) in order to obtain a sufficient jumping height when the movement is successful while the knee joint is rapidly extended to perform a jump when movement fails. In the single landing section after the jump (i.e. phase 4), if the ankle joint rapidly dorsiflexed after take-off and the hip joint rapidly flexed, so landing was not successful. Conversely, in a successful landing movement, muscle activity of the biceps femoris was greatly activated resulting no shaking in the last landing section (i.e. phase 5). Conclusion: In order to succeed in this movement, it is necessary to perform a strong jump after rapidly descending the center of gravity of the body using the force of the biceps femoris muscle. Further improvement of the skills on the balance beam requires the analysis of the game-like situation with continuous research on kinematic and kinematic analysis of various techniques, jumps, turns, etc.

• Advances in aircraft and spacecraft science
• /
• 제2권4호
• /
• pp.391-401
• /
• 2015

Crashworthiness design and certification have been and will continue to be the main concern in aviation safety. The effects of roll angles on fuselage section crashworthiness for typical civil transport category aircrafts were investigated. A fuselage section with waved-plates under cargo floor is suggested, and the finite element model of fuselage section is developed to simulate drop test subjected to 7 m/s impact velocity under conditions of 0-deg, 5-deg, 10-deg and 15-deg roll angles, respectively. A comparative analysis of failure modes, acceleration responses, and energy absorption of fuselage section under various conditions are given. The results show that the change of roll angles will significantly affect fuselage deformation, seat peak overloads, and energy absorption. The crashworthiness capability of aircraft can be effectively improved by choosing appropriate landing way.

• 한국정밀공학회지
• /
• 제26권10호
• /
• pp.47-55
• /
• 2009

In this study, a robot foot having toes for firm stepping on uneven surface is proposed. The toes are connected to the lower leg by parallel links so that the lower leg can rotate in the rolling and pitching directions during stance phase without ankle joint. The landing performance of the foot on uneven surface was evaluated by relative comparison with that of the most common foot making point contact with the walking surface, since the test conditions considering real uneven surface could be hardly defined for its objective evaluation. Anti-slip margin(ASM) was defined in this study to express the slip resistance of a robot foot when it lands on a projection with half circular-, triangular- or rectangular cross section, assuming that uneven surface consists of projections having these kind of cross sections in different sizes. Based on the ASM analysis, the slip conditions for the two feet were experimentally confirmed. The results showed that the slip resistance of the new foot is not only higher than that of the conventional point contact type foot but also less sensitive to the surface friction coefficient.

• 한국산학기술학회논문지
• /
• 제15권4호
• /
• pp.2335-2342
• /
• 2014

미래 유통 혁신 및 도심에서의 긴급 차량 운행에 도움을 주고자 차량 이동 정보 등이 포함된 실시간 교통 상황 정보 및 긴급 정보 제공 등을 위하여 무인 쿼드로터의 사용하고자 할 경우 무인 쿼드로터의 사용 안전성을 충분히 고려해야 한다. 따라서 본 연구에서는 4개의 모터를 가지고 있고 시스템적으로 구조적 균형이 잘 잡혀있는 무인 쿼드로터 시스템의 안전성 증대를 위하여 도심에서의 안전 착륙 제어에 대한 연구를 무인 쿼드로터 시스템의 비선형 특성을 고려한 운동학 및 동역학적 모델 기반 및 외란이나 시스템 비선형성에 강인한 Fuzzy 제어기를 통하여 진행하고자 하며, 이를 컴퓨터 시뮬레이션을 통하여 분석 하였다.

• 한국도로학회논문집
• /
• 제15권6호
• /
• pp.49-60
• /
• 2013

PURPOSES : The evaluation of the pavement condition of the asphalt concrete pavement of No. 2 runway of Inchon International Airport through PMS, a supporting system for making a decision of pavement, maintenance and repair, was made, and the proper time for repair according to the PCI reduction rate was suggested. METHODS : By comparing and analyzing the evaluation results of pavements built in 2009, 2010, 2011, PCI change in each facility (No. 2 runway, C parallel taxiway, connection taxiway) was calculated. By applying the calculated change to PCI deduction rate model, the pavement condition of the target sections was estimated, and then the necessary section and time for repair were chosen. RESULTS : After careful consideration of the time for pavement and maintenance, based on the result of PCI prediction, it was estimated that the southern takeoff and landing section of No. 2 runway was required to be repaired in 2012; connection taxiway in 2013; and C parallel taxiway in 2014; however, the section which is the main moving route of connection taxiway and C parallel taxiway was needed to be repaired in 2012. CONCLUSIONS : For maintenance and repair of airport pavements, the optimal alternative should be chosen by considering economics and operability, via examining the time for repair and the aspect of management all together on the basis of this study.

• 한국항공우주학회지
• /
• 제46권10호
• /
• pp.845-855
• /
• 2018

최대 이륙중량 55 kg에 최대 순항속도가 180 km/h이고 수직이착륙이 가능한 쿼드 틸트 프롭로터 무인기에 적용할 프롭-블레이드 단면 설계를 수행하였다. 먼저 프롭-블레이드 단면 설계수행을 위한 설계 프로세스를 수립하고 단면 설계에 필요한 요구도를 식별하였으며 식별된 요구도 만족을 위한 단면 설계를 수행하였다. 단면 설계 결과를 분석하기 위하여 유한요소 단면해석 프로그램을 활용하여 인장/굽힘/뒤틀림 강성 및 단위길이 당 중량, 탄성 축 등을 포함한 주요설계 인자들을 도출하였으며, 이 과정에서 프롭-블레이드의 설계 중량을 예측하였다. 그리고 도출된 설계 인자들을 로터시스템 통합 해석 프로그램에 적용하여 프롭-블레이드 운영 환경에서의 동적 안정성을 분석하였으며, 로터시스템 통합 해석 프로그램을 통해 분석된 프롭-블레이드 하중을 활용하여 2차원 단면 구조 해석을 수행하여 프롭-블레이드 구조 안전성을 확인하였다. 이러한 단면 설계/해석 과정에서 설계 요구도를 만족시키지 못하거나 다른 구성품에 부정적 영향을 준 설계 결과에 대해서는 설계 변경을 수행하였으며, 이를 통해 요구도를 만족시켰다.

• 한국항해항만학회:학술대회논문집
• /
• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
• /
• pp.33-37
• /
• 2006

Since 1993, the civil aviation community through RTCA (Radio Technical Commission for Aeronautics) and the ICAO (International Civil Air Navigation Organization) have been working on the definition of GNSS augmentation systems that will provide improved levels of accuracy and integrity. These augmentation systems have been classified into three distinct groups: Aircraft Based Augmentation Systems (ABAS), Space Based Augmentation Systems (SBAS) and Ground Based Augmentation Systems (GBAS). The last one is an implemented system to support Air Navigation in CAT-I approaching operation. It consists of three primary subsystems: the GNSS Satellite subsystem that produces the ranging signals and navigation messages; the GBAS ground subsystem, which uses two or more GNSS receivers. It collects pseudo ranges for all GNSS satellites in view and computes and broadcasts differential corrections and integrity-related information; the Aircraft subsystem. Within the area of coverage of the ground station, aircraft subsystems may use the broadcast corrections to compute their own measurements in line with the differential principle. After selection of the desired FAS for the landing runway, the differentially corrected position is used to generate navigation guidance signals. Those are lateral and vertical deviations as well as distance to the threshold crossing point of the selected FAS and integrity flags. The Department of Applied Science in Naples has create for its study a virtual GBAS Ground station. Starting from three GPS double frequency receivers, we collect data of 24h measures session and in post processing we generate the GC (GBAS Correction). For this goal we use the software Pegasus V4.1 developed from EUROCONTROL. Generating the GC we have the possibility to study and monitor GBAS performance and integrity starting from a virtual functional architecture. The latter allows us to collect data without the necessity to found us authorization for the access to restricted area in airport where there is one GBAS installation.

• Journal of Astronomy and Space Sciences
• /
• 제38권1호
• /
• pp.55-63
• /
• 2021

The universe is well known to be consists of dark energy, dark matter and the standard model (SM) particles. The dark matter dominates the density of matter in the universe. The dark matter is thought to be linked with dark photon which are hypothetical hidden sector particles similar to photons in electromagnetism but potentially proposed as force carriers. Due to the extremely small cross-section of dark matter, a large amount of data is needed to be processed. Therefore, we need to optimize the central processing unit (CPU) time. In this work, using MadGraph5 as a simulation tool kit, we examined the CPU time, and cross-section of dark matter at the electron-positron collider considering three parameters including the center of mass energy, dark photon mass, and coupling constant. The signal process pertained to a dark photon, which couples only to heavy leptons. We only dealt with the case of dark photon decaying into two muons. We used the simplified model which covers dark matter particles and dark photon particles as well as the SM particles. To compare the CPU time of simulation, one or more cores of the KISTI-5 supercomputer of Nurion Knights Landing and Skylake and a local Linux machine were used. Our results can help optimize high-energy physics software through high-performance computing and enable the users to incorporate parallel processing.